Scrambling sequence design for embedding receiver ID into frozen bits for blind detection

ABSTRACT

Methods and devices are described for encoding and decoding control information that has been modulated based on one or more identifiers of the transmitter and/or receiver. Some embodiments describe scrambling sequence design for multi-mode block discrimination on downlink control information (DCI) blind detection. Separate scrambling masks may be applied to disparate bit fields within a coded DCI message, wherein each of the scrambling masks is derived from a unique identifier associated with either the transmitter or the intended receiver. The scrambling masks may be used by the receiver to perform early termination of the decoding process, to mitigate intercell interference, and to verify that the receiver is the intended receiver.

PRIORITY CLAIM

This application is a continuation of U.S. application Ser. No.15/852,761 titled “Scrambling Sequence Design for Embedding UE ID intoFrozen Bits for DCI Blind Detection” and filed on Dec. 22, 2017, whichclaims benefit of priority to U.S. Provisional Application No.62/442,225 titled “Early Termination with Polar Codes for eMBB DCI BlindDetection” and filed on Jan. 4, 2017, U.S. Provisional Application No.62/455,448 titled “Early Block Discrimination with Polar Codes toFurther Accelerate DCI Blind Detection” and filed on Feb. 6, 2017, U.S.Provisional Application No. 62/501,493 titled “Early BlockDiscrimination with Polar Codes to Further Accelerate DCI BlindDetection” and filed on May 4, 2017, and U.S. Provisional ApplicationNo. 62/521,946 titled “Scrambling Sequence Design for Multi-Mode BlockDiscrimination on DCI Blind Detection” and filed on Jun. 19, 2017, allof which are hereby incorporated by reference in their entirety as iffully and completely set forth herein.

FIELD OF THE INVENTION

The field of the invention generally relates to encoders and decodersused in wireless communications.

Description of the Related Art

Decoders are used in many areas of wireless communications. Atransmitter may encode a message which is intended for reception by aspecific receiver. If the intended receiver does not have a prioriknowledge of where (e.g., where in time and/or frequency) to look forthe encoded message, it may undergo a blind decoding procedure to searcha set of candidate locations for the intended message.

Blind decoding can take considerable time and computational resources,as the receiver may have to perform blind decoding on messages in alarge number of candidate locations before the correct message isdecoded. Accordingly, improvements in the field are desired.

SUMMARY OF THE EMBODIMENTS

Various embodiments are described of systems and methods for encodingand decoding control information that has been modulated based on one ormore identifiers of the transmitter and/or receiver. Some embodimentsdescribe scrambling sequence design for multi-mode block discriminationon downlink control information (DCI) blind detection. Separatescrambling masks may be applied to disparate bit fields within a codedDCI message, wherein each of the scrambling masks is derived from aunique identifier associated with either the transmitter or the intendedreceiver. The scrambling masks may be used by the receiver to performearly termination of the decoding process, to mitigate intercellinterference, and to verify that the receiver is the intended receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1 is a diagram illustrating a wireless communication environment,according to some embodiments.

FIG. 2 is a diagram illustrating a wireless communication environmentwith base station coverage overlap, according to some embodiments.

FIG. 3 is a block diagram illustrating an exemplary base station,according to some embodiments.

FIG. 4 is a block diagram illustrating an exemplary UE, according tosome embodiments.

FIG. 5 is a schematic diagram of various communication channels used foruplink and downlink communication, according to some embodiments;

FIG. 6 is a graph of mutual information of bits in a polar code as afunction of bit index, according to some embodiments;

FIG. 7 is a flow diagram illustrating an exemplary method for atransmitter to encode a message that has been modulated based on one ormore identifiers, according to some embodiments;

FIG. 8 is a flow diagram illustrating an exemplary method for decodingan encoded message, and demodulating the decoded bits based on anidentifier, according to some embodiments;

FIG. 9 is a graph of the tradeoff between latency and power consumptionfor parallelized processing, according to some embodiments;

FIG. 10 shows two data plots of cumulative workload for successivecancellation list decoding as a function of bit index, according to someembodiments;

FIG. 11 illustrates an example of channel polarization, where n=11;

FIG. 12 illustrates an example polar encoder, where n=3;

FIG. 13 illustrates an example polar decoder, where n=3;

FIG. 14 is a flowchart diagram illustrating DCI encoding as prescribedfor LTE;

FIG. 15 is a flowchart diagram illustrating DCI encoding adapted toincorporate polar codes, according to some embodiments;

FIG. 16 illustrates bit-mask assignment patterned after that used byLTE, according to some embodiments;

FIG. 17 illustrates a proposed NR bit-mask assignment, according to someembodiments;

FIG. 18 illustrates a successive bit-mask assignment, according to someembodiments;

FIG. 19 illustrates data using a moving average to obtain early blockdiscrimination for a mismatch (top) and match (bottom), according tosome embodiments;

FIG. 20 illustrates the effect of bit feedback on match identificationusing a running average to obtain early termination for a mismatch (top)and match (bottom), according to some embodiments; and

FIG. 21 illustrates the combined effects of sequence mismatch and errorpropagation for early termination for a mismatch (top) and a match(bottom), according to some embodiments.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Incorporation by Reference

The following references are hereby incorporated by reference in theirentirety as though fully and completely set forth herein:

1. “Polar Code Construction for NR”, Huawei, HiSilicon, 3GPP TSG RAN WG1Meeting #86bis, October 2016.

2. Alexios Balatsoukas-Stimming, Mani Bastani Parizi, and Andreas Burg,“LLR-Based Successive Cancellation List Decoding of Polar Codes”, IEEETransactions on Signal Processing, October 2015.

3. 3GPP TS 36.211: “Evolved Universal Terrestrial Radio Access (E-UTRA);Physical Channels and Modulation”.

4. Provisional Patent Application No. 62/455,448, titled “Early BlockDiscrimination with Polar Codes to Further Accelerate DCI BlindDetection”.

5. Provisional Patent Application No. 62/501,493, titled “Early BlockDiscrimination with Polar Codes to Further Accelerate DCI BlindDetection”.

6. U.S. patent application Ser. No. 15/359,845, titled “MemoryManagement and Path Sort Techniques in a Polar Code SuccessiveCancellation List Decoder”.

Terms

The following is a glossary of terms used in the present application:

Memory Medium—Any of various types of memory devices or storage devices.The term “memory medium” is intended to include an installation medium,e.g., a CD-ROM, floppy disks, or tape device; a computer system memoryor random access memory such as DRAM, DDR RAM, SRAM, EDO RAM, RambusRAM, etc.; or a non-volatile memory such as a magnetic media, e.g., ahard drive, optical storage, or ROM, EPROM, FLASH, etc. The memorymedium may comprise other types of memory as well, or combinationsthereof. In addition, the memory medium may be located in a firstcomputer in which the programs are executed, and/or may be located in asecond different computer which connects to the first computer over anetwork, such as the Internet. In the latter instance, the secondcomputer may provide program instructions to the first computer forexecution. The term “memory medium” may include two or more memorymediums which may reside in different locations, e.g., in differentcomputers that are connected over a network.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical or opticalsignals.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable or hardwired interconnect. Examples include FPGAs (FieldProgrammable Gate Arrays), PLDs (Programmable Logic Devices), FPOAs(Field Programmable Object Arrays), and CPLDs (Complex PLDs). Theprogrammable function blocks may range from fine grained (combinatoriallogic or look up tables) to coarse grained (arithmetic logic units orprocessor cores). A programmable hardware element may also be referredto as “reconfigurable logic”.

Application Specific Integrated Circuit (ASIC)—this term is intended tohave the full breadth of its ordinary meaning. The term ASIC is intendedto include an integrated circuit customized for a particularapplication, rather than a general purpose programmable device, althoughan ASIC may contain programmable processor cores as building blocks.Cell phone chips, MP3 player chips, and many other single-function ICsare examples of ASICs. An ASIC is usually described in a hardwaredescription language such as Verilog or VHDL.

Program—the term “program” is intended to have the full breadth of itsordinary meaning. The term “program” includes 1) a software programwhich may be stored in a memory and is executable by a processor or 2) ahardware configuration program useable for configuring a programmablehardware element or ASIC.

Software Program—the term “software program” is intended to have thefull breadth of its ordinary meaning, and includes any type of programinstructions, code, script and/or data, or combinations thereof, thatmay be stored in a memory medium and executed by a processor. Exemplarysoftware programs include programs written in text-based programminglanguages, e.g., imperative or procedural languages, such as C, C++,PASCAL, FORTRAN, COBOL, JAVA, assembly language, etc.; graphicalprograms (programs written in graphical programming languages); assemblylanguage programs; programs that have been compiled to machine language;scripts; and other types of executable software. A software program maycomprise two or more software programs that interoperate in some manner.

Hardware Configuration Program—a program, e.g., a netlist or bit file,that can be used to program or configure a programmable hardware elementor ASIC.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), grid computing system, or other device or combinationsof devices. In general, the term “computer system” can be broadlydefined to encompass any device (or combination of devices) having atleast one processor that executes instructions from a memory medium.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thusthe term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, i.e., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

DETAILED DESCRIPTION

FIG. 1—Wireless Communication Environment

FIG. 1 illustrates an exemplary (and simplified) wireless environmentthat includes multiple communication systems. FIG. 1 shows an examplecommunication system involving a base station (BS) 102 communicatingwith a plurality of user equipment devices (UEs) 106A-C. The basestation 102 may be a cellular base station which performs cellularcommunications with a plurality of wireless communication devices.Alternatively, the base station 102 may be a wireless access point forperforming Wi-Fi communications, such as according to the 802.11standard or related standards. The UEs 106 may be any of various devicessuch as a smart phone, tablet device, computer system, etc. One or bothof the base station 102 and the wireless communication device 106 mayinclude decoder logic as described herein.

In the illustrated embodiment, different UEs and the base station areconfigured to communicate via a broadcast network and/or apacket-switched cellular network. It is noted that the system of FIG. 1is merely one example of possible systems, and embodiments may beimplemented in any of various systems, as desired.

Cellular base station 102 may be a base transceiver station (BTS) orcell site, and may include hardware that enables wireless communicationwith the UEs 106A-C. The base station 102 may also be configured tocommunicate with a core network. The core network may be coupled to oneor more external networks, which may include the Internet, a PublicSwitched Telephone Network (PSTN), and/or any other network. Thus, thebase station 102 may facilitate communication between the UE devices106A-C and a network.

Base station 102 and other base stations operating according to the sameor different radio access technologies (RATs) or cellular communicationstandards may be provided as a network of cells, which may providecontinuous or nearly continuous overlapping service to UEs 106A-C andsimilar devices over a wide geographic area via one or more RATs.

The base station 102 may be configured to broadcast communications tothe UEs 106A-C. The term “broadcast” herein may refer to one-to-manytransmissions that are transmitted for receiving devices in a broadcastarea rather than being addressed to a particular device. Further,broadcast transmissions are typically unidirectional (from transmitterto receiver). In some situations, control signaling (e.g., ratingsinformation) may be passed back to a broadcast transmitter from thereceivers, but the content data is transmitted in only one direction. Incontrast, cellular communication is typically bi-directional. “Cellular”communications also may involve handoff between cells. For example, whenUE 106A (and/or UEs 106B-C) moves out of the cell served by cellularbase station 102, it may be handed over to another cellular base station(and the handover may be handled by the network, including operationsperformed by base station 102 and the other cellular base station). Incontrast, when a user moves from the range covered by a first broadcastbase station to the range covered by a second broadcast base station, itmay switch to receiving content from the second broadcast base station,but the base stations do not need to facilitate handover (e.g., theysimply continue broadcasting and do not care which base station aparticular UE is using).

Traditionally, broadcast transmissions are performed using differentfrequency resources than cellular transmissions. In some embodiments,however, frequency resources are shared between these different types oftransmissions. For example, in some embodiments, a broadcast basestation is configured to relinquish one or more frequency bands duringscheduled time intervals for use by a cellular base station forpacket-switched communications.

In some embodiments, control signaling transmitted by a broadcast orcellular base station may allow end user devices to maintain fullsignaling connectivity (which may eliminate network churn), extendbattery life (e.g., by determining when to remain in a low power modewhen a base station is not transmitting), and/or actively managecoverage detection (e.g., rather than perceiving spectrum sharingperiods as spotty coverage or a temporary network outage).

The base station 102 and the UEs 106A, 106B, and 106C may be configuredto communicate over the transmission medium using any of various RATs(also referred to as wireless communication technologies ortelecommunication standards), such as LTE, 5G New Radio (NR), NextGeneration Broadcast Platform (NGBP), W-CDMA, TDS-CDMA, and GSM, amongpossible others such as UMTS, LTE-A, CDMA2000 (e.g., 1× RTT, 1× EV-DO,HRPD, eHRPD), Advanced Television Systems Committee (ATSC) standards,Digital Video Broadcasting (DVB), etc.

Broadcast and cellular networks are discussed herein to facilitateillustration, but these technologies are not intended to limit the scopeof the present disclosure and the disclosed spectrum sharing techniquesmay be used between any of various types of wireless networks, in otherembodiments.

FIG. 2—Wireless Communication Environment with Multiple Base Stations

FIG. 2 illustrates an exemplary wireless communication system thatincludes base stations 102A and 102B which communicate over atransmission medium with one or more user equipment (UE) devices,represented as UEs 106A-106C. The communication environment in FIG. 2may function similarly to that described in FIG. 1, above. However, FIG.2 illustrates that the center UE 106B may operate within range of bothof the base stations 102A and 102B. In these embodiments, UE 106B maymistakenly receive a communication from base station 102B when it wasintending to receive communications from base station 102A. This effectmay be referred to as intercell interference, and embodiments hereindescribe novel methods for efficiently avoiding intercell interferencein cell coverage overlap areas.

FIG. 3—Base Station

FIG. 3 illustrates an exemplary block diagram of a base station 102. Insome embodiments, base station 102 may be a broadcast base station suchas base station 102A of FIG. 2 and/or a cellular base station such asbase station 102B of FIG. 2. It is noted that the base station of FIG. 3is merely one example of a possible base station. As shown, the basestation 102 may include processor(s) 304 which may execute programinstructions for the base station 102. The processor(s) 304 may also becoupled to memory management unit (MMU) 340, which may be configured toreceive addresses from the processor(s) 304 and translate thoseaddresses to locations in memory (e.g., memory 360 and read-only memory(ROM) 350) or to other circuits or devices.

The base station 102 may include at least one network port 370. Thenetwork port 370 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 106, access to thetelephone network as described above. In some embodiments, the networkport 370 (or an additional network port) may be coupled to a televisionnetwork and configured to receive content for broadcasting. The networkport 370 (or an additional network port) may also or alternatively beconfigured to couple to a cellular network, e.g., a core network of acellular service provider. The core network may provide mobility relatedservices and/or other services to a plurality of devices, such as UEdevices 106. In some cases, the network port 370 may couple to atelephone network via the core network, and/or the core network mayprovide a telephone network (e.g., among other UE devices 106 servicedby the cellular service provider).

The base station 102 may include at least one antenna 334. The at leastone antenna 334 may be configured to operate as a wireless transceiverand may be further configured to communicate with UE devices 106 viaradio 330. The antenna 334 communicates with the radio 330 viacommunication chain 332 in the illustrated embodiment. Communicationchain 332 may be a receive chain, a transmit chain or both. The radio330 may be configured to communicate via various RATs.

The processor(s) 304 of the base station 102 may be configured toimplement part or all of the methods described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively, theprocessor 304 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit), or a combination thereof. In someembodiments, the processor, MMU, and memory may be a distributedmultiprocessor system. For example, the processor system may comprise aplurality of interspersed processors and memories, where processingelements (also called functional units) are each connected to aplurality of memories, also referred to as data memory routers. Theprocessor system may be programmed to implement the methods describedherein.

In some embodiments, base station 102 is configured to perform bothbroadcast and bi-directional packet-switched communications. In theseembodiments, base station 102 may include multiple radios 330,communication chains 332, and/or antennas 334, for example. In otherembodiments, the disclosed spectrum sharing techniques may be performedby different base stations configured to perform only broadcasttransmissions or only packet-switched communications.

FIG. 4—User Equipment (UE)

FIG. 4 illustrates an example simplified block diagram of a UE 106. TheUE 106 may be any of various devices as defined above. UE device 106 mayinclude a housing which may be constructed from any of variousmaterials.

As shown, the UE 106 may include a system on chip (SOC) 400, which mayinclude portions for various purposes. The SOC 400 may be coupled tovarious other circuits of the UE 106. For example, the UE 106 mayinclude various types of memory (e.g., including NAND flash 410), aconnector interface 420 (e.g., for coupling to a computer system, dock,charging station, etc.), the display 460, wireless communicationcircuitry 430 such as for LTE, 5G New Radio (NR), GSM, Bluetooth (BT),WLAN, and/or broadcast, etc. The UE 106 may further comprise one or moresmart cards that implement SIM (Subscriber Identity Module)functionality. The wireless communication circuitry 430 may couple toone or more antennas, such as antenna 435.

As shown, the SOC 400 may include processor(s) 402 which may executeprogram instructions for the UE 106 and display circuitry 404 which mayperform graphics processing and provide display signals to the display460. The processor(s) 402 may also be coupled to memory management unit(MMU) 440, which may be configured to receive addresses from theprocessor(s) 402 and translate those addresses to locations in memory(e.g., memory (e.g., read only memory (ROM) or another type of memory)406, NAND flash memory 410) and/or to other circuits or devices, such asthe display circuitry 404, wireless communication circuitry 430,connector I/F 420, and/or display 460. The MMU 440 may be configured toperform memory protection and page table translation or set up. In someembodiments, the MMU 440 may be included as a portion of theprocessor(s) 402. In some embodiments, the processor, MMU, and memorymay be a distributed multiprocessor system. For example, the processorsystem may comprise a plurality of interspersed processors and memories,where processing elements (also called functional units) are eachconnected to a plurality of memories, also referred to as data memoryrouters. The processor system may be programmed to implement the methodsdescribed herein.

In some embodiments (not shown), UE 106 is configured to receivewireless broadcasts, e.g., from broadcast base station 102A of FIG. 2.In these embodiments, UE 106 may include a broadcast radio receiver. Insome embodiments, UE 106 is configured to receive broadcast data andperform packet-switched cellular communications (e.g., LTE) at the sametime using different frequency bands and/or the same frequency resourcesduring different time slices. This may allow users to view TV broadcastswhile performing other tasks such as browsing the internet (e.g., in asplit-screen mode), using web applications, or listening to streamingaudio. In other embodiments, the disclosed techniques may be used insystems with devices that are configured as broadcast receivers or forcellular communications, but not both.

The processor(s) 402 of the UE device 106 may be configured to implementpart or all of the features described herein, e.g., by executing programinstructions stored on a memory medium (e.g., a non-transitorycomputer-readable memory medium). In some embodiments, the processor(s)402 may comprise a multiprocessor array of a plurality of parallelizedprocessing elements. For example, the processor(s) 402 may be designedin accordance with the HyperX architecture described in detail inReference 6, or another parallel processor architecture. In theseembodiments, separate ones of the parallelized processing elements maybe configured to perform decoding procedures on separate respective bitpaths of a successive cancellation list (SCL) decoding procedure, orthey may be configured to perform decoding procedures on separateencoded messages in parallel, for example. Alternatively (or inaddition), processor(s) 402 may be configured as a programmable hardwareelement, such as an FPGA (Field Programmable Gate Array), or as an ASIC(Application Specific Integrated Circuit). Alternatively (or inaddition) the processor(s) 402 of the UE device 106, in conjunction withone or more of the other components 400, 404, 406, 410, 420, 430, 435,440, 460 may be configured to implement part or all of the featuresdescribed herein.

UE 106 may have a display 460, which may be a touch screen thatincorporates capacitive touch electrodes. Display 460 may be based onany of various display technologies. The housing of the UE 106 maycontain or comprise openings for any of various elements, such asbuttons, speaker ports, and other elements (not shown), such asmicrophone, data port, and possibly various types of buttons, e.g.,volume buttons, ringer button, etc.

The UE 106 may support multiple radio access technologies (RATs). Forexample, UE 106 may be configured to communicate using any of variousRATs such as two or more of Global System for Mobile Communications(GSM), Universal Mobile Telecommunications System (UMTS), Code DivisionMultiple Access (CDMA) (e.g., CDMA2000 1×RTT or other CDMA radio accesstechnologies), Long Term Evolution (LTE), LTE Advanced (LTE-A), 5G NR,and/or other RATs. For example, the UE 106 may support at least tworadio access technologies such as LTE and GSM. Various different orother RATs may be supported as desired.

In some embodiments, UE 106 is also configured to receive broadcastradio transmissions which may convey audio and/or video content. Instill other embodiments, a UE 106 may be configured to receive broadcastradio transmissions and may not be configured to perform bi-directionalcommunications with a base station (e.g., UE 106 may be a media playbackdevice).

UE-Specific Control Messages

In current cellular communication systems, a base station may broadcasta plurality of control messages (e.g., downlink control information(DCI) messages, or other encoded control information) that are eachintended for reception by a specific user equipment device (UE).

FIG. 5 is a schematic diagram of various channels in downlink (DL) anduplink (UL) that are currently in use in some cellular communicationtechnology standards (e.g., in LTE). As illustrated, DCI messages may beincluded in the physical downlink control channel (PDCCH), which maycomprise a shared search space servicing a plurality of UEs. Embodimentsherein describe DCI messages that are typically sent over PDCCH.However, it may be appreciated by one of skill in the art how similarmethods may be used in any of a variety of other communication channels(e.g., such as the other illustrated channels of FIG. 5), wherein a basestation transmits UE-specific messages that may need to be disambiguatedby a large number of serviced UEs (e.g., the physical broadcast channel,PBCH, may also be used to transmit this type of message, among otherpossibilities).

To ensure that the correct UE receives a particular message, in someembodiments, the base station may append a cyclic redundancy check (CRC)at the end of the control message. In some embodiments, the base stationmay scramble a CRC that is attached to certain downlink controlinformation (DCI) messages according to a user equipment identifier (UEID).

In these embodiments, if the wrong UE (e.g., a UE with a different UE IDthan that used to scramble the CRC) attempts to descramble the CRC, itmay result in a CRC error and the message may be dropped. Thus, only theUE with a matching UE ID may be able to correctly descramble the CRC andacknowledge the DCI message. If a UE receives a message in a resourceblock for which the CRC is unsuccessful, the UE may assume that themessage is destined for another user and drop the message.

While appending a scrambled CRC to a control message may be an effectiveway to verify that the message is received by the correct UE, the methodtypically requires that the entire control message is decoded before thecheck can be performed. Embodiments described herein improve on thismethodology by enabling early termination for a mismatched UE ID duringthe decoding process. Embodiments herein further improve on thismethodology by mitigating inter-cell interference by scrambling a subsetof the control message based on a CELL ID.

According to some embodiments, a proposed method leverages properties ofpolar codes whereby information known to the transmitter and receivercan be inserted in frozen bits and/or information bits to expedite IDverification. For example, a shortcoming of typical CRC methods is thatthe UE cannot verify the CRC until after the entire message has beendecoded. By leveraging properties of polar codes, embodiments describedherein allow a UE to determine whether a message was intended for the UEbefore the decoding process is completed. If it is determined that themessage is not intended for the UE, the UE may undergo “earlytermination”, and abandon (or abort) the decoding process.

Early termination with PC (parity-check) polar codes may be derived fromthe potential to place a known, agreed (between an assignedtransmitter/receiver (TX|RX) pair) pattern in frozen bits, startingafter the first information bit (e.g., starting after puncturing). Theencoder (transmitter) may insert a bit field containing a unique patternknown both to TX and RX. For example, the transmitter may modulate asubset of the frozen bits and/or information bits with an identifier bitfield (alternatively called “check bits”). Throughout this disclosure,modulating a first set of bits with a second set of bits may beunderstood to correspond to performing an exclusive-OR (XOR) operationbetween the bits in the same relative positions within each of the twosets of bits. The bit field may be interrogated at the RX by some means,(e.g. path metric reliability, log likelihood ratio (LLR) growth, harddecision decoding, or another metric) to determine whether the currentRX is the intended recipient of the packet in question.

The receiver may otherwise use the known bit values just as it would afield of all zeros in decoding the surrounding information bits.Decoding may cease if a match to the intended recipient is not foundusing one of the methods described above. In other words, given thesuccessive nature of polar decoding, the RX need not decode the entirepacket to determine whether the check bits match its assigned ID.

Different criteria may be used to determine where to place theidentifier bit field among the frozen bits, according to variousembodiments. One possibility is to place the identifier bit field infrozen bits following the first information bit, as complexity can besignificantly reduced if the decoder is able to bypass the first severalfrozen bits on the presumption that they are all zero. Additionally, itmay be determined how many bits should be assigned to the check bits.The more bits assigned, the more reliable the detectability may become,but the longer the decoder may remain active before it can terminate.Additionally, it may be determined how deep into the block to insert theidentifier bit field, based on increasing channel reliability with bitindex. The depth of placement may be decided jointly with how many checkbits to employ. The deeper into the block, the more reliable theunderlying check bits, however, the longer the decoder may run beforeearly termination can be determined.

For example, FIG. 6 illustrates the mutual information as a function ofbit index for a particular implementation of polar codes. Asillustrated, the later bit indices contain a larger amount of mutualinformation (e.g., they are more reliable), but additional latency isincurred if the identifier is inserted later in the polar code. Thepoint of puncturing is illustrated by the thin black vertical lines,while frozen bits and information bits are illustrated as thin dark greyand light grey vertical lines, respectively. The mutual information (MI)trend 16 (thick black solid line) illustrates the mutual informationobtained when averaging over 16 bits at a time, and the MI trend 32(thick grey solid line) illustrates the mutual information obtained whenaveraging over 32 bits at a time.

In some embodiments, the modulated frozen bits may be selected such thatthey occur within the control information after an information bit witha predetermined threshold level of reliability. In some embodiments, themodulated frozen bits are selected to balance a reliability and alatency associated with decoding of the encoded modulated controlinformation by a UE.

Alternatively, in some embodiments, a pseudorandom sequence generatedfrom the UE ID may be used to modulate the frozen bits to help areceiver discern blocks meant for it versus those destined for anotheruser. Advantageously, this may be done without affecting the code rate,user throughput or decoding reliability. Given the limited extent of theUE ID relative to the typical number of available frozen bits, themethod may use a scrambling ‘mask’ with a pseudorandom bit sequence thatmatches the extent of the frozen bit field, wherein the pseudorandom bitsequence is based on the UE ID. In other words, the transmitter maygenerate a pseudorandom sequence of bits based on the UE ID, wherein thepseudorandom sequence of bits is the same length as the frozen bitfield. The transmitter may then modulate all of the frozen bits with thepseudorandom sequence of bits.

In current cellular communication systems (e.g., LTE, and potentiallyNR), a base station (i.e. eNodeB or eNB) may multiplex DCIs for multipleUEs in a set of predefined candidate locations. This places a particularburden on the UE which, employing a blind detection procedure, mayinterrogate each candidate location to identify the DCIs intended for itversus those meant for other users. Blind detection is typically used indownlink communications, because a base station often services a largenumber of UEs, and may be unable to dedicate specific radio resources toeach of the serviced UEs. Rather, the base station may transmitUE-specific information (such as DCI, or other downlink controlinformation) in a shared set of candidate locations, and each UE mayperform blind detection on the candidate locations to determine if aparticular message was intended for it.

Embodiments herein expedite the blind detection procedure, as the basestation may scramble the frozen bits of a polar code with a UE-specificmask to facilitate user identification. In some embodiments, theinformation bits of the DCI may additionally be scrambled according to acell-specific mask to mitigate adjacent cell interference.

While embodiments herein may be described in reference to a base stationin communication with a UE device, it can be readily understood that themethods described may be generally applied to many different kinds oftransmitters and receivers. In particular, any transmitter/receiver pairmay benefit from implementation of embodiments described herein, if thetransmitter is attempting to transmit communications to a particularreceiver, wherein there is a need for the receiver to verify both oreither of: a) the identification of the transmitter and/or b) that thetransmission was intended for the particular receiver.

Embodiments herein describe a scrambling sequence design that builds onthe objectives set forth by LTE and, leveraging attributes unique topolar codes, extends the design capabilities to include multi-mode blockdiscrimination with the potential for early termination in a unifiedframework. In some embodiments, separate masks are assigned torespective portions of the polar code construction, each with a distinctpurpose: UE identification, early termination of blind decoding tominimize energy expended on blocks not intended for the present user,and/or adjacent cell interference mitigation. Early termination of blinddecoding may advantageously reduce overall energy consumption for mobiledevices.

In some embodiments, methods are presented that retain the CRCscrambling used by LTE. In some embodiments, a UE-specific pseudo-randomsequence (e.g., a pseudo-random binary sequence or another type ofpseudo-random sequence, as described in further detail below) insertedin the polar code frozen bit-field enables early termination. Theseembodiments may improve on previous implementations, wherein the entiremessage has to be decoded before the CRC may be performed. Givensuperior cross-correlation properties, the pseudo-random sequence (PRS)may provide improved code separation beyond that afforded by CRCscrambling alone.

In some embodiments a second PRS mask, derived from the CELL ID, isapplied to the information bit field affording cell separation analogousto that available with LTE. In some embodiments, each of the first andsecond PRS masks may be applied together as an ensemble in a unifieddiscrimination mask that simultaneously enables user identification withearly termination as well as adjacent cell interference mitigation.

FIG. 7—Modulating and Encoding Control Information

FIG. 7 illustrates a flow chart diagram for a method for modulating andencoding a message by a transmitter, according to some embodiments. Insome embodiments, separate scrambling masks may be applied to each of aplurality of different blocks within an encoded message. Each of theseparate scrambling masks may serve to verify by the receiver anidentity of either the transmitter or the receiver. For example, and asdescribed in greater detail below, both the transmitter and the receivermay be preconfigured with knowledge of the transmitter and/or receiveridentities, such that the receiver may be able to selectively demaskrespective blocks of the scrambled message. In some embodiments, thetransmitter may be a base station and the receiver may be a userequipment device (UE). Alternatively, both the transmitter and receivermay be UEs.

In some embodiments, a transmitter may employ a polar coding scheme toencode a message that is intended for a specific receiver. In someembodiments, the encoded message may be a downlink control information(DCI) message, although other types of control messages, and in generalany type of transmitted message may be used according to embodimentsdescribed herein. While embodiments herein may be described in terms ofDCI messages, it may be appreciated by those of skill in the art thatthe described embodiments may be generalized to other types oftransmitted control messages and other types of messages (e.g., payloadmessages).

Polar coding, as described in greater detail below, divides (or‘polarizes’) a plurality of communication channels into more reliableand less reliable channels. The more reliable channels are often used tocarry the payload information of the communication, and these bits ofthe communication are often referred to as ‘information bits’. In someembodiments, the transmitter may append a sequence of cyclic redundancycheck (CRC) bits at the end of the information bits. The less reliablechannels typically contain reference bits that are known to both thetransmitter and the receiver, commonly referred to as ‘frozen bits’. Thefrozen bits may be utilized by the receiver to facilitate the decodingprocess.

While embodiments herein are described in terms of polar codes, it maybe appreciated that the methods described may also be applied to variousother coding schemes. For example, embodiments herein may be applied toother types of forward error correction (FEC) codes, and more generallyto any type of encoded message.

At 702, the transmitter may represent UE-specific control information astwo or more sequences of bits. In various embodiments, the two or moresequences of bits may be contiguous, non-contiguous, or may partiallyoverlap. In some embodiments, the transmitter may be configured toencode messages using polar codes, and the two or more sequences of bitsmay include frozen bits, information bits, and/or cyclic redundancycheck (CRC) bits.

At 704, the transmitter may modulate one or more of the sequences ofbits based on one or more identifiers. In some embodiments, the one ormore identifiers may identify the transmitter (e.g., CELL ID or basestation ID) and/or the receiver (e.g., UE ID). In some embodiments, apseudorandom sequence (PRS) may be derived from the identifier(s), andthe identifier(s) may be known to both the transmitter and receiver. Asdescribed in further detail below, each of the one or more identifiersmay be used to generate a respective pseudorandom sequence that isgenerated to be the same length as the respective subset of encoded bitsfor which the pseudorandom sequence will be applied as a scramblingmask.

In some embodiments, modulating the one or more of the sequences of bitsbased on the one or more identifiers may involve applying separatescrambling ‘masks’ to modulate the sequences of bits based on theidentifier(s). The application of a scrambling mask may involvemodulating each sequence of bits with a PRS of bits generated from arespective identifier. For example, a UE ID corresponding to theintended receiver may be used to generate a first pseudorandom sequencePRS that is the same length as the length of a frozen bit sequence in apolar code. The first PRS may be used to modulate the frozen bits of thepolar code. In other embodiments, the first PRS may be the same lengthas a subset of frozen bits, and may be used to modulate only the subsetof frozen bits. Alternatively, a subset of the frozen bits may bedirectly modulated by the UE ID.

In the case where only a subset of the frozen bits is modulated based onthe UE ID (or the PRS generated from the UE ID), the subset of frozenbits to be modulated may be selected such that those frozen bits occurwithin the control information after an information bit with apredetermined threshold level of reliability. For example, later bits inpolar coding are more reliable, and the modulated subset of frozen bitsmay be selected such that the subset of bits occurs late enough to havea predetermined threshold level of reliability. Selecting a subset offrozen bits for modulation that occurs later in the control informationalso introduces additional latency into the decoding procedure. In someembodiments, the subset of frozen bits may be selected to balance areliability and a latency associated with decoding of the encodedmodulated control information by a UE.

The UE ID, or the PRS generated based on the UE ID, may be used tomodulate the frozen bits while not modulating the information bits. Inother words, the UE ID may be used to selectively modulate only thefrozen bits, and not the information bits, of the control information.

Alternatively or in addition, a CELL ID of the transmitter may be usedto generate a second PRS that is the same length as the length of theinformation bit sequence of a polar code. The second PRS may be used tomodulate the information bits of the polar code. Advantageously,modulating the information bit sequence based on the pseudorandomsequence generated from the base station identifier may mitigateadjacent cell interference experienced by UEs that receive the encodedmodulated control information. For example, a first UE may be located ina service area of two or more base stations, and a UE ID used for thefirst UE by a first base station (e.g., a base station upon which thefirst UE is camped) may additionally be used as a UE ID for another(second) UE by a second base station (e.g., a base station upon whichthe first UE may receive broadcast messages but is not camped). In thiscase, the first UE may mistake a message intended for the second UE asintended for the first UE (e.g., because the same UE ID is used forboth). In the example, modulating the information bit sequence based ona base station identifier may allow the first UE to determine whether aparticular message has originated from the correct base station (e.g.,the base station upon which the first UE is camped).

Alternatively or in addition, a UE ID corresponding to the intendedreceiver may be used to generate a third PRS that is the same length asthe CRC bits that are appended to a polar coded message. The third PRSmay be used to modulate the CRC mask, such that the CRC mask isgenerated based on the UE ID. For example, the information bits may beappended with a cyclic redundancy check (CRC) scrambled with a CRC maskbased on the UE ID, which may be performed prior to modulating theinformation bits. This may offer an additional check by the receiverthat the receiver is the intended recipient of the message.

At 706, the two or more sequences of bits may be encoded to produce anencoded message. For example, the modulated frozen bits, informationbits, and/or CRC bits may be encoded using polar codes to produceencoded modulated control information, which may comprise the encodedmessage. The encoded modulated control information may be transmitted toone or more UEs for performing downlink control information (DCI) blinddetection.

At 708, the transmitter may transmit the encoded message to the receiver(e.g., in a wireless manner). The transmission may occur using any of avariety of wireless communication technologies, as described variouslyin the present disclosure.

FIG. 8—Decoding and Demodulating an Encoded Message

FIG. 8 is a flow chart diagram illustrating a method for decoding anddemodulating an encoded message (e.g., coded data, or polar coded datareceived from a remote transmitter) by a receiver, according to someembodiments. The receiver may be a user equipment device (UE) comprisinga radio, a non-transitory computer-readable memory medium, and aprocessor (e.g., as described above in reference to FIG. 4), or it maybe another kind of receiver.

At 802, the receiver may receive the encoded message from a transmitterin a wireless manner. The encoded message may comprise coded dataincluding an encoding of one or more sequences of bits (e.g., a firstsequence of bits and potentially a second and third sequence of bits).The receiver may have knowledge of each of the identifiers used by thetransmitter to modulate respective subsets of bits of the encodedmessage. The encoded message may be a polar coded message, and the oneor more sequences of bits may include a sequence of frozen bits, asequence of information bits, and/or a sequence of cyclic redundancycheck (CRC) bits. The encoded message may be received and decoded (e.g.,as described in detail below) as part of a downlink control information(DCI) blind detection procedure.

The receiver may proceed to implement a decoding procedure on the codeddata, as described in further detail below in reference to steps804-814. The decoding procedure may be a successive cancellation listdecoding procedure, or any of a variety of other decoding procedures.

At 804, the receiver may begin a decode of the encoded message toproduce a subset of the first sequence of bits. The first sequence ofbits may be frozen bits of a polar code, so that the decoding procedurebegins by decoding a subset of the frozen bits, for example.

The decoded subset of bits may be used (e.g., as described in moredetail below in reference to steps 806-810) to verify whether theencoded message was intended for the receiver. In some embodiments, theparticular subset of bits that is used in this subsequent IDverification may be selected to balance a reliability and a latencyassociated with the decoding procedure. For example, in embodimentswherein the encoded message is a polar coded message and the firstsequence of bits are frozen bits of the polar code, frozen bits thatoccur later in the decoded message may have a higher reliability thanearlier frozen bits, but these later frozen bits will not be decodeduntil later in the decoding process. The particular subset of frozenbits used for ID verification may be selected to balance the desirableincrease in reliability with the undesirable increase in latencyassociated with later occurring frozen bits of the decoded message.

At 806, the receiver may demodulate the decoded subset of the firstsequence of bits with a first pseudorandom sequence (PRS) generated froma first identifier. For example, the receiver may be a UE that may use afirst PRS generated from the UE's ID to demodulate the decoded subset offrozen bits of a polar coded message. The receiver may generate thefirst PRS, which may be the same PRS that was previously generated bythe transmitter. In these embodiments, the transmitter may havepreviously scrambled the frozen bits using the same PRS, such that thereceiver may unscramble the scrambling mask by demodulating the decodedsubset of frozen bits based on the PRS. The PRS may be the same lengthas the entire frozen bit field, but the demodulation may be performedusing the subset of the PRS that corresponds to the decoded subset offrozen bits.

At 808, the receiver may perform a cross-correlation calculation betweenthe subset of bits that have been decoded and a respective sequence ofreference bits. For example, the transmitter and the receiver may bepreconfigured to know which values the demodulated frozen bits shouldhave (e.g., the frozen bits may be known by the transmitter and receiverto be a string of zeros or another sequence of values), and these valuesmay be stored as a sequence of reference bits on a memory of thereceiver. In these embodiments, a strong cross-correlation between thedecoded frozen bits and the respective sequence of reference bits mayindicate to the receiver that the demodulation of the frozen bits wasperformed with the correct UE ID. In some embodiments, thecross-correlation calculation may involve calculating a divergence ofpath metrics associated with the subset of decoded frozen bits and thecorresponding subset of reference bits.

In some embodiments, the cross-correlation may be performed afterdemodulating using the PRS, but in other embodiments the sequence ofreference bits may be based on the first identifier, and thedemodulation step 806 may be skipped. In other words, rather thandemodulating the decoded subset of bits based on the first identifier(or based on a PRS generated from the first identifier), thecross-correlation may be performed with reference bits that aregenerated based on the first identifier, so that the demodulation isimplicitly accomplished through the cross-correlation calculation. ThePRS may be the same length as the entire frozen bit field, but thedemodulation may be performed using the subset of the PRS thatcorresponds to the decoded subset of frozen bits.

At 810, the receiver may compare the result of the cross-correlationcalculation to a correlation threshold. The correlation threshold may bea predetermined degree of correlation, which may or may not varydepending on the number of bits used in the cross-correlationcalculation.

At 812, if the result of the cross-correlation calculation is below thepredetermined correlation threshold, the receiver may determine that thedemasking procedure was unsuccessful (e.g., because the message wasintended for a different receiver with a different UE ID), and thereceiver may abort the decoding procedure. In some embodiments, and asdescribed in further detail below, the receiver may maintain a runningaverage calculation of the cross-correlation as more frozen bits aredecoded, and the receiver may continue the decoding procedure unless theresults of the cross-correlation calculation fall below thepredetermined correlation threshold. In some embodiments, after abortingthe decoding procedure, the receiver may receive a second encodedmessage (e.g., it may receive a second polar coded message in a wirelessmanner from a base station), and the receiver may implement the decodingprocedure (e.g., repeating steps 804-810) on the second polar codedmessage.

At 814, if the result of the cross-correlation calculation is above thepredetermined correlation threshold, the receiver may continue thedecoding procedure. For example, it may complete the decoding of thefirst sequence of bits (e.g., the frozen bits) and/or continue to decodethe second sequence of bits (e.g., the information bits).

After decoding the second sequence of bits, the receiver may demodulatethe second sequence of bits with a second pseudorandom sequencegenerated from a second identifier. For example, in the case where thesecond sequence of bits are information bits of a polar code, theinformation bits may have been scrambled using a second PRS generatedfrom an identifier unique to the transmitter (e.g., a base station ID).In these embodiments, the receiver may demodulate (e.g., unscramble) thedecoded information bits using the same second PRS. The receiver maythen store the demodulated second sequence of bits as a decoded messagein the memory medium.

When the receiver has finished decoding and demodulating the secondsequence of bits (e.g., the information bits), the receiver may performa cyclic redundancy check (CRC) to determine if an error has occurredduring the decoding process. In some embodiments, the cyclic redundancycheck may be performed using CRC bits that are appended at the end ofthe information bits. The CRC bits may have been scrambled using a PRSderived from an identifier that is unique to the intended receiver(e.g., its UE ID), and the receiver may unscramble the CRC bits using athird PRS generated from the receiver identifier. Alternatively, the CRCbits may have been scrambled directly with the identifier that is uniqueto the intended receiver (e.g., its UE ID), and the receiver mayunscramble the CRC bits using the receiver identifier. In theseembodiments, multiple layers of identity verification may be employed tomitigate intercell interference and ensure that the receiver receivesthe intended message. For example, if either of the UE ID or the CELL IDused by the receiver to generate respective PRSs is different from theUE ID or CELL ID used by the transmitter to modulate the message, thecyclic redundancy check may result in an error and the message may bedropped. If the CRC indicates that an error has occurred, the receivermay determine that the message may have been received from a transmitterwith an identifier different from the transmitter identifier used by thereceiver. The receiver may then abandon the message and monitor anotherchannel or network resource (e.g., a different control element) toperform blind decoding on a subsequent message.

Explaining this process in further detail, upon receipt of a block whosecheck bits match that to which the UE is assigned, metrics internal tothe decoder will accumulate coherently when using check bit values inplace of the corresponding frozen bits. If instead the check bits do notmatch the values the decoder has determined to use in place of thefrozen bits corresponding to the check bits, the metrics will not growas expected. Based on this observation, this decode instance can beterminated as it presumably does not coincide with the intended DCIencoding.

In some embodiments, the receiver may be configured with a plurality ofparallelized processors (e.g., the HyperX architecture described inReference 6, or another parallel processor architecture), and each ofthe parallel processors may be configured to simultaneously perform oneor more of steps 804-808 on separate received encoded messages. Theparallel processors may dynamically reallocate computational resourcesas separate received encoded messages become decoded and/or abandoned.The receiver may receive multiple encoded messages, and separate ones ofthe parallelized processing elements may implement decoding procedureson each of the received one or more additional encoded messages.Alternatively, or in addition, separate ones of the parallelizedprocessors may be configured to assist in decoding a single encodedmessage, to decrease decoding time. In some embodiments, and asdescribed in further detail below, the decoding procedure may be asuccessive cancellation list (SCL) decoding procedure; and separate onesof the plurality of parallelized processors may be configured to performdecoding procedures on separate respective bit paths of the SCL decodingprocedure.

If a particular encoded message is determined by a particular processorto not be intended for the receiver (e.g., if receiver determines toabort the decoding procedure at 810), the processor may be redirected toinitiate a decoding procedure on another (second) received encodedmessage. Conversely, if a particular processor is successful in decodinga received message, the plurality of parallelized processors may abandontheir respective decoding procedures and enter a low-power state ordormant state.

Multiple decoder instances may be enabled in parallel to reducedetection latency at the expense of added power consumption. In thegeneral case, each decoder may run to completion before determiningwhich among the active decoders has identified a valid decoding (e.g.,based on a CRC check). Control block processing and data payloadprocessing may have different latency and throughput requirements. Theimplemented degree of parallelization may be separately adjusteddepending on the current workload, to obtain a desirable balance oflatency and throughput for the current application. For example, thedegree of parallelization (e.g., the number of concurrently activeparallel processors) may be different during the decoding of controlinformation (e.g., steps 804-810) than during subsequent or previousprocessing of payload data.

Early termination has potential to mitigate the added power consumptionby halting certain decode instances based on the coherence of the checkbits encountered in the course of decoding the block. Additionally,because the computational complexity per decoded bit may increase overtime in a successive cancellation list decoder (e.g., because the numberof paths being simultaneously decoded increases with the bifurcation ofthe bit paths), early termination may decrease computation time at arate that is faster than linear in the terminated bit position. Forexample, terminating a decoding process after half of the bits have beendecoded may shorten the decode time by more than half relative to acomplete decode, because the second half of the bits may take longer todecode than the first half. This effect is illustrated schematically inFIG. 9. As illustrated, increased parallelization simultaneously leadsto increased power consumption and decreased latency from the increasednumber of active processing elements (solid thick curved arrow).However, implementing early termination enables a larger reduction inlatency given a similar increase in power consumption (dashed curvedarrow).

The lower diagram of FIG. 9 additionally illustrates schematically howthe processing power requirements for decoding polar coded bits increasewith the bit index. This effect is illustrated in more detail in FIG.10, which uses actual data from two implementations of a successivecancellation list (SCL) decoder (described in further detail below). Asillustrated, the cumulative work associated with the SCL decoderaccelerates as a function of the bit index, for a code rate of R=⅙ (leftgraph) and R=⅓ (right graph).

Polar Codes

This section describes in further detail the function and structure ofpolar codes, according to various embodiments. A method of constructingcapacity achieving codes for the memoryless binary symmetric channel isknown in the art. The resulting polar codes leverage a phenomenon knownas channel polarization (see FIG. 11) resulting from a recursive processby which the channel capacity, i.e. maximum mutual information, tendstoward 1 (fully available) or 0 (unavailable). The corresponding bitprobabilities, 1 and 0.5, respectively, approach their limits as thecode length, N=2^(n), increases with positive integer values n. Data maybe transferred by placing information on bits on the most reliablechannels (these bits may be referred to as information bits) while bitsplaced on the least reliable channels may be set to a fixed value, e.g.0 or another known value or set of values. These bits may be referred toas frozen bits. Frozen bits and their mapping to the code matrix may beknown by both the transmitter and receiver. As a result, frozen bits maybe used as a reference by a decoding algorithm to determine whether anerror has occurred from noise in the communication channel, orotherwise. For example, the known values of the frozen bits may becompared to the values determined through the decoding algorithm, todetermine whether an error has occurred.

Successive Cancellation Algorithm

The successive cancellation (SC) decoder has been used to demonstratethe viability of the polar coding method. While offering low complexitydecoding, the decoder requires long block sizes, approaching a million(i.e. 2²⁰) bits, in order to compete with rival Turbo or Low DensityParity Check (LDPC) Codes. The successive nature of the SC decoderadditionally imposes significant limitations on decoder throughput.However, as may be appreciated by one of skill in the art, any of thedecoding processes described herein may be implemented according to a SCdecoding methodology.

Successive Cancellation List Algorithm

An improved method for decoding polar codes has been established, whichis called Successive Cancellation List (SCL) decoding. SCL decodinginspects two possibilities at each decoder phase in parallel: û_(φ)=0and û_(φ)=1 for each non-frozen bit. The decoder may pursue multiplepaths in parallel, retaining the most likely paths at each stage. Theencoder may also append a cyclic redundancy check (CRC) that isultimately used in determining the appropriate bit decision from theavailable L paths, see Balatsoukas-Stimming et al. in reference 2 above.As may be appreciated by one of skill in the art, any of the decodingprocesses described herein may be implemented according to a SCLdecoding methodology. Additionally, a concatenated SCL decodingmethodology may be employed.

Polar Codes

Polar codes form a class of linear block codes described by a generatormatrix, G. Polar codes of block lengths N may be generated according to:G=F _(N)

(F ₂)^(⊗n)

Where F_(N) denotes the Kronecker product of

${F_{2} = \begin{pmatrix}1 & 0 \\1 & 1\end{pmatrix}},$among other possibilities.

A polar code is defined by the location of k information bits and (N-k)frozen bits in a block of length, N. The code rate,

$R = \frac{k}{N}$is expressed as the ratio of non-frozen bits to the block length. Thecode rate can be adjusted linearly by varying the number of non-frozenbits per block. Typically, the block length, N, is chosen to be a powerof two, such that N=2^(n), where n is a natural number.FIG. 12—Exemplary Polar Encoder

FIG. 12 shows a sample polar code construction for block length N=2³.The encoder begins with inputs, u_(i), which are encoded into outputs,x_(i). Information bits are shown in bold. The remaining inputs may beassigned frozen bit values, 0. At each stage, s, the encoder combinespairs of bits according to the encoding tree shown to the right, where ⊗indicates an exclusive-OR (XOR) operation.

SC Decoder

The SCL decoder may be viewed as a collection of SC decoders, eachemploying independent min-sum calculations on a row of the accumulatedlog likelihood ratio (LLR) statistics. In some embodiments, an SCdecoder may proceed as follows:

At each bit position, i, the SC decoder aims to estimate the bit u_(i)as follows:

${\hat{u}}_{i}\overset{\Delta}{=}\left\{ \begin{matrix}{0,} & {{{{if}\mspace{14mu} i} \in A_{c}},} \\{0,} & {{{{if}\mspace{14mu}{\ln\left( \frac{\left. {\Pr\left( {y,{\hat{u}}_{0}^{i - 1}} \right)} \middle| u_{i} \right. = 0}{\left. {\Pr\left( {y,{\hat{u}}_{0}^{i - 1}} \right)} \middle| u_{i} \right. = 1} \right)}} \geq 0},} \\{1,} & {otherwise}\end{matrix} \right.$where

$\ln\left( \frac{\left. {\Pr\left( {y,{\hat{u}}_{0}^{i - 1}} \right)} \middle| u_{i} \right. = 0}{\left. {\Pr\left( {y,{\hat{u}}_{0}^{i - 1}} \right)} \middle| u_{i} \right. = 1} \right)$computes the log likelihood ratio (LLR) at bit position, i, for theestimated information vector, û, given received symbol, y, andpreviously decoded bits {û₀, û₁, . . . , û_(i-1)}, and A_(c) indicatesthe frozen bit positions.

FIG. 13 shows an example decoder where n=3, so that the block lengthN=2³.

The decoder algorithm is applied recursively to the multi-stage diagramillustrated in FIG. 13 according to the following:

$\lambda_{l,i}\overset{\Delta}{=}\left\{ \begin{matrix}{{\lambda_{f}\left( {\lambda_{{l + 1},i};\lambda_{{l + 1},{i + 2}}^{n - l - 1}} \right)},} & {{if}\mspace{14mu}\frac{i}{2^{l}}\mspace{14mu}{is}\mspace{14mu}{even}} \\{{\lambda_{g}\left( {{\hat{s}}_{l,z};\lambda_{{l + 1},i};\lambda_{{l + 1},{i + 2}}^{n - l - 1}} \right)},} & {otherwise}\end{matrix} \right.$

Where λ_(l,i) denotes the LLR of row i and stage l of the SC decodergraph. The associated kernel calculations constitute the min-sumalgorithm:λ_(f)(λ_(a), λ_(b))=sgn(λ_(a))·sgn(λ_(b))·min(|λ_(a)|, |λ_(b)|)λ_(g)(ŝ, λ _(a), λ_(b))=λ_(a)(−1)^(ŝ)+λ_(b)SCL Decoder

A list decoder may depart from the baseline SC decoder with theintroduction of a path metric update. At the completion of eachbit-decoding stage, path metrics may be updated accounting for thepossibility of both possible bit values: û_(i)=0 and û_(i)=1. In someembodiments, a sorting operation may be performed to rank the paths inthe list by their likelihood of being a correctly decoded string. The‘tree’ of possible paths may then be pruned, retaining only the L mostlikely paths. The cycle of LLR calculations and path extension andpruning may be repeated for each bit in a transmission block, at whichpoint the most likely path is chosen, revealing the best estimate of thepayload data bits.

The SCL decoders described in reference 2 above use the results of thesorting operation to direct multiple memory copies (memcpy), addingprocessing overhead as the LLR updates cannot resume until the memcpyoperations have completed.

DCI Blind Detection

In some embodiments, user identification is based on an assigned C-RNTI(Cell Radio Network Temporary Identifier). Embodiments herein describemethods to discriminate blocks intended for the present user versusthose intended for another user early in the course of block decoding.

In some embodiments, cell-specific scrambling is used to mitigate theeffects of adjacent cell interference.

In some embodiments, methods described herein may function atsignal-to-noise ratios (SNRs) below that for the accompanying shareddata channels. Additionally, some embodiments may reduce the false alarmrate (FAR) compared to previous implementations.

Candidate Search Spaces

LTE defines a set of Control Channel Element (CCE) locations for a UE tointerrogate in search of intended Physical Downlink Control Channel(PDCCH) communications. The set of CCE locations are divided into UESpecific Search Spaces (UESS) and Common Search Spaces (CSS) asindicated in Table 1.

TABLE 1 LTE DCI Search Spaces Search Aggregation Size No. of PDCCH No.of Candidate Space Level (L) (in CCEs) Candidates Blind Decodes UESS 1 66 12 2 12 6 12 4 8 2 4 8 16 2 4 UESS: 16 32 CSS 4 16 4 8 8 16 2 4 CSS: 612 Total: 44

With LTE, each UE may receive up to 2 DCI formats from UESS perTransmission Time Interval (TTI). One reference DCI format, e.g. format0/1A, is typically expected regardless of the transmission modeconfigured for the UE. Defined to have the same payload size, thereference DCI formats may require a single decoding attempt percandidate location regardless of the underlying format type. Each UE mayrequire one additional decoding attempt per UESS candidate location forone of DCI formats 1, 1B, 1D, 2, 2A, 2B, depending upon the configuredtransmission mode, every TTI. A UE may then require 16×2=32 blinddecoding attempts to monitor all UESS candidate locations for twodifferent possible DCI formats per TTI.

DCI formats 0/1A and 3/3A (if TPC-PUCCH-RNTI or TPC-PUSCH-RNTI isconfigured), specified to have the same payload size, may require oneblind decoding attempt per candidate PDCCH location in the CSS. Anadditional decoding attempt is needed per candidate location in the CSSfor DCI format 1C when the UE is required to receive PDCCH scrambledwith the SI-RNTI (System Information), P-RNTI (Paging), or RA-RNTI(Random Access), resulting in 6×2=12 blind decoding attempts across theavailable CSS candidate locations. In total, up to 12+32=44 blinddecoding attempts may be required per TTI to monitor both the CSS andUESSS for the assigned DCI formats. Because each of the up to 44 blinddecoding attempts requires considerable time and computationalresources, enabling early termination during the blind decoding processmay considerably improve the user experience.

FIG. 14—Block Discrimination

FIG. 14 illustrates DCI encoding as prescribed for LTE. LTE employs twomethods of block discrimination on DCI detection as depicted in FIG. 14,which as explained in further detail below (e.g., in reference to FIG.15), may be superimposed on the polar code structure. FIG. 14illustrates a tail-biting convolutional encoder, which may be replacedby a polar code methodology for block discrimination, according to someembodiments.

First, a user-specific CRC mask may be applied at the end of each PDCCHand provides block separation based on UE ID. Second, a cell-specificscrambling mask may be applied at the encoder output to modulate theoutput message based on CELL ID, where the encoder is represented inFIG. 16 by an icon of the nth Kronecker power matrix, Gn.

Polar Code Construction for PDCCH

Taking the underlying polar code structure into account, embodimentsdescribed herein perform a multi-mode discrimination mask that can beadapted to a downlink control channel.

The proposed sequence design starts with a conventional Polar Codeconstruction where a code of length N=2^(n) assigns k information bits(inclusive of CRC and/or Parity Check (PC) bits), A ⊂[N], and N-k frozenbits, F=[N]\A, the assigned values of which are known a priori to thereceiver. The code rate, R=k/N, is determined by the number of user datadependent information bits relative to the block size.

In some embodiments, individual fields of the underlying polar code canbe assigned to facilitate block discrimination according to some or allof the following three methodologies.

First, as explained above, a 16-bit CRC may be appended to each PDCCHfor error detection. The CRC may be scrambled with a UE-specific mask toenable identification of which PDCCH(s) are intended for a given UE uponinterrogating the list of candidate PDCCH locations.

Secondly, as explained above, a UE ID, or bit values derived from afunction of the UE ID, may be inserted in the frozen bit field toadditionally permit a UE to discriminate early in the course of blockdecoding the PDCCH(s) intended for it from those destined for anotheruser. As a form of early termination, UE ID insertion is intended toreduce energy expended decoding blocks not meant for the present UE.

Third, as explained above, the information bits may be masked with acell-specific mask (CELL ID mask) to mitigate the effects ofadjacent-cell interference.

FIG. 15—Bit Mask Assignment

FIG. 15 illustrates DCI adapted to incorporate polar codes (potentiallyin NR), according to some embodiments. FIG. 15 illustrates the separateapplication of bit masks to each of frozen bits, information bits, andCRC bits, respectively, in a polar coded message. As illustrated, themulti-mode mask assignment separately uses different subsets of the bitfield for separate identification purposes.

Given a linear transform, application of the Kronecker matrix can bedistributed to relate the assigned bit mask(s) to the encoder output:(w+u)G=wG+uG,

Here plus (+) represents a bit-wise XOR of the resulting scramblingmask, wG, computed once per DCI instance, with the original encoderoutput, uG. The bit masks, s_(0:F-1), r_(0:D-1), x_(rnti,0:15), appliedin succession at the encoder input as illustrated in FIG. 16 areequivalent to the scrambling mask, wG, applied at the encoder output,where 0_(0:M-1) represents an all zero vector of length M, and G relatesa scrambling mask, w, at the encoder input to the encoder output. Thecombined mask can be similarly removed at the receiver prior todecoding. Properties assigned to a mask at the encoder input manifestequivalently in a corresponding mask applied at the encoder output.Individual attributes can be assigned so that each mask produces anintended effect as referenced to the construction at the encoder input.The mask contributions may then be combined, encoded, and then appliedat the encoder output without loss in effectiveness.

FIGS. 17-18: Successive Bit-Mask Assignment

FIGS. 17-18 illustrate bit-mask assignment patterned after that used byLTE, according to some embodiments. In traditional LTE, pseudorandomsequence generation is adapted for a variety of purposes (See reference3). An exemplary method for generating a pseudorandom sequence isillustrated here to indicate that this method or one similar can beapplied to fill the frozen bit contents, the initialization of which isbased on the representation of the UE ID. The method of pseudorandomsequence generation specified by LTE may be adapted to form the frozenbit contents initialized by C-RNTI to facilitate early discriminationwith DCI blind detection. In some embodiments, a second application mayform the information bit mask initialized on the CELL ID.

c_(n) = (x_(n + N_(c))⁽¹⁾ + x_(n + N_(c))⁽²⁾)mod 2, n = 0, 1, …  , M_(PN) − 1

Here N_(c)=1600 and M_(PN) is determined by the number of affectedfrozen bits.

Sequences x_(n) ¹ and x_(n) ² may be generated as follows:x _(n+31) ⁽¹⁾=(x _(n+3) ⁽¹⁾ +x _(n) ⁽¹⁾)mod2, n=0, 1, . . . , M _(PN) +N_(c)−31x _(n+31) ⁽²⁾=(x _(n+3) ⁽²⁾ +x _(n+2) ⁽²⁾ +x _(n+1) ⁽²⁾ +x _(n)⁽²⁾)mod2, n=0, 1, . . . , M _(PN) +N _(c)−31

Here x_(n) ¹ and x_(n) ² may be initialized as follows:

x₀⁽¹⁾ = 1, x_(n)⁽¹⁾ = 0, n = 1, 2, …  , 30${\sum\limits_{0}^{30}{x_{n}^{(2)} \cdot 2^{n}}} = {c_{init} = {{\left\lfloor \frac{n_{s}}{2} \right\rfloor \times 2^{9}} + N_{ID}^{UE}}}$

The frozen bit contents are filled according to:

-   -   w_(m)=c_(n), where m∈F beyond the first information bit

Extending the pseudorandom sequence length to the number of availablefrozen bits provides early user separation in a deterministic andreliable manner. If the entirety of the frozen bit contents arepopulated with the UE ID-derived pseudorandom sequence, a reliable andefficient means of early block discrimination may be obtained.Similarly, a pseudorandom sequence may be derived from the CELL ID andapplied as a bit mask to the information portion of the block.Additionally or alternatively, the CRC may be masked based on theassigned RNTI as is done in LTE. After applying the appropriate zeropadding and then summing the masks, their combined effect may be appliedin a single scrambling sequence at the encoder output.

FIG. 19—Early Block Discrimination Based on UE ID Frozen Bit Assignment

FIG. 19 illustrates data for an early termination procedure of frozenbit decoding, for the case of both a match and a mismatch between theencoding and decoding UE ID.

Given a UE ID derived frozen bit assignment, early block discriminationmay amount to Maximum Likelihood (ML) sequence detection. A match in theasserted frozen bit position yields a positive accumulation, while amismatch yields a negative accumulation. A predominance of positiveaccumulation as seen by a moving average (MA) provides a reliable meansto discriminate those blocks meant for the current user from those meantfor another user. This tendency persists even at low SNR, as shown inFIG. 19.

For the purposes of block discrimination, the best LLRs are taken to bethe set seen at each bit position as belonging to the best path, i.e.the path exhibiting the smallest path metric. There is no assertion thatthe perceived best path during the course of block decoding will surviveas the remaining best path. However, indication of the perceived bestpath may prove useful in deriving metrics to facilitate earlydiscrimination.

As illustrated in FIG. 19, a moving average of the best LLRs exhibits anincreasing trend upon match in frozen bit assignment and trends downwardwhen there is a mismatch in expected bit assignment. Referring again toFIG. 19, the top two plots correspond to a mismatch in frozen bitassignment between encoder and decoder. As expected, the accumulatedLLRs exhibit a sharp downward trend as the number of negative matchesbegins to accumulate. The onset of this downturn is a function of thelength of the applied moving average. It occurs earlier with a shortermoving average and later with a longer moving average.

Examining a match in encoder/decoder frozen bit assignment, we observethat the LLR accumulation is largely positive. This observation is againa function of the length of the applied moving average (MA). Asillustrated in the bottom two plots of FIG. 19, a relatively shortmoving average, e.g. MA[8], MA[16], is susceptible to short-livedfluctuations rendering the metric less reliable for blockdiscrimination. Ultimately, a tradeoff can be found in MA size thatbalances power savings due to early block discrimination and thereliability of the mechanism used to make that determination.

FIG. 20—Effect of Bit Feedback on Match Identification

FIG. 20 illustrates the effect of erroneous feedback on the matchidentification procedure. A mismatch in frozen bit assignment has asecondary effect related to expected decoder operation. The SC and SCLdecoders are characterized by a succession of f and g-operators. Whilethe f-operator depends solely on input LLRs, the g-operator output isconditioned on the preceding bit estimates:

f(a, b) = minsum(a, b);${g\left( {\hat{s},a,b} \right)} = \begin{matrix}{{b - a},} & {\hat{s} = 1} \\{{b + a},} & {else}\end{matrix}$

If a portion of the previously estimated bits, fed back in the form ofpartial sums to the g-operator, are in error due to a mismatch in frozenbit assignment, the downstream LLRs may be affected as well in a mannerthat is incremental to disturbance due to the channel itself. The datain FIG. 20 is taken at relatively high SNR, and as illustrated the LLRsin the bottom right-hand plot predominantly trend in the positivedirection whereas those in the upper right-hand plot show the disruptiveeffects of the channel coupled with erroneous feedback in theg-operator. Erroneous feedback in the g-operator propagates todownstream bit decoding, frozen and info-bits alike, further reducingFAR should an unintended PDCCH elude early termination and make its wayto a final CRC check. In particular, the effects of frozen bit mismatchpersist even in the event that the scrambling mask is removed prior tothe start of decoding.

FIG. 21—Combined Effects of Sequence Mismatch and Error Propagation

FIG. 21 illustrates how the combined effects of sequence mismatch anderror propagation due to g-operator feedback give rise to heuristicsthat may prove useful for early block discrimination. In particular, themoving average of the best LLR for a UE ID mismatch (top) oscillatesbetween positive and negative values without exhibiting a clear positivetrend, while the moving average of the best LLR for a UE ID match(bottom) steadily climbs as a function of the frozen bit index.

CONCLUSIONS

Embodiments herein describe a method of frozen bit assignment that maybe used in polar code construction to facilitate early blockdiscrimination on DCI blind detection. The proposal leverages a propertyunique to polar codes that permits use of frozen bit contents to conveyuser ID, and/or information bit contents to convey CELL ID. Thestructure is further leveraged to provide cell separation in a mannerthat meets the objectives set for LTE. The end result is a scramblingsequence that enables both CELL ID and UE ID with the added benefit ofearly termination. Replicated at the decoder, this imprinting is usefulin discerning blocks intended for a particular receiver amid multiplecandidate PDCCHs, most of which are destined by design for some otheruser.

The reliability of block determination, including the decision toabandon decoding, improves as a function of bit position in accordancewith the underlying channel reliability. The approach is compatible withPC, CRC or hybrid methods of code construction still underconsideration. The proposed method of embedding UE ID imposes minimalchanges in presumed encoder and decoder implementations. It furtherprovides wide latitude in algorithm design, permitting receivermanufacturers to trade power savings for reliability of earlytermination.

Embodiments of the present disclosure may be realized in any of variousforms. For example, in some embodiments, the present invention may berealized as a computer-implemented method, a computer-readable memorymedium, or a computer system. In other embodiments, the presentinvention may be realized using one or more custom-designed hardwaredevices such as ASICs. In other embodiments, the present invention maybe realized using one or more programmable hardware elements such asFPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of the methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a computing device may be configured to include aprocessor (or a set of processors) and a memory medium, where the memorymedium stores program instructions, where the processor is configured toread and execute the program instructions from the memory medium, wherethe program instructions are executable to implement any of the variousmethod embodiments described herein (or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets). Thedevice may be realized in any of various forms.

Although specific embodiments have been described above, theseembodiments are not intended to limit the scope of the presentdisclosure, even where only a single embodiment is described withrespect to a particular feature. Examples of features provided in thedisclosure are intended to be illustrative rather than restrictiveunless stated otherwise. The above description is intended to cover suchalternatives, modifications, and equivalents as would be apparent to aperson skilled in the art having the benefit of this disclosure.

The scope of the present disclosure includes any feature or combinationof features disclosed herein (either explicitly or implicitly), or anygeneralization thereof, whether or not it mitigates any or all of theproblems addressed herein. Accordingly, new claims may be formulatedduring prosecution of this application (or an application claimingpriority thereto) to any such combination of features. In particular,with reference to the appended claims, features from dependent claimsmay be combined with those of the independent claims and features fromrespective independent claims may be combined in any appropriate mannerand not merely in the specific combinations enumerated in the appendedclaims.

What is claimed is:
 1. A transmitter comprising: a radio; and aprocessor coupled to the radio; wherein the radio and the processor areconfigured to: represent receiver-specific control information as aplurality of frozen bits and a plurality of information bits of a polarcode; modulate at least a subset of the plurality of frozen bits basedon a receiver-specific identifier to produce modulated controlinformation, wherein at least the subset of the plurality of frozen bitsare selected for modulation whereby at least the subset of the pluralityof frozen bits occur within the control information after an informationbit with a predetermined threshold level of reliability, wherein theplurality of information bits of the control information is notmodulated based on the receiver-specific identifier; encode themodulated control information using the polar code to obtain encodedmodulated control information; and wirelessly transmit the encodedmodulated control information.
 2. The transmitter of claim 1, whereinthe radio and the processor are further configured to: generate apseudorandom sequence of bits based on the receiver-specific identifier,wherein the pseudorandom sequence of bits is the same length as theplurality of frozen bits, wherein modulating at least a subset of theplurality of frozen bits based on the receiver-specific identifiercomprises modulating the plurality of frozen bits with the pseudorandomsequence of bits.
 3. The transmitter of claim 1, wherein at least thesubset of the plurality of frozen bits are selected to balance areliability and a latency associated with decoding of the encodedmodulated control information by a receiver.
 4. The transmitter of claim1, wherein the encoded modulated control information is transmitted toone or more receivers for performing downlink blind detection.
 5. Areceiver, comprising: a radio; and a processor coupled to the radio;wherein the receiver is configured to: receive a first polar codedmessage in a wireless manner from a transmitter, the first polar codedmessage comprising an encoding of a plurality of frozen bits and aplurality of information bits; implement a decoding procedure on thefirst polar coded message, wherein, in implementing the decodingprocedure, the receiver is configured to: begin a decode of the firstpolar coded message to produce a subset of the frozen bits; perform across-correlation calculation based on the subset of the frozen bits anda corresponding subset of reference bits, wherein the reference bits arebased on an identifier of the receiver; abort the decoding procedurebased on a determination that the result of the cross-correlationcalculation is below a cross-correlation threshold.
 6. The receiver ofclaim 5, wherein the reference bits are a pseudorandom sequence of bitsgenerated from the identifier of the receiver, wherein the pseudorandomsequence of bits is the same length as the plurality of frozen bits. 7.The receiver of claim 5, wherein the subset of the plurality of frozenbits is selected to balance a reliability and a latency associated withthe decoding procedure.
 8. The receiver of claim 5, wherein the firstpolar coded message is received and the decoding procedure is initiatedas part of a downlink blind detection procedure.
 9. The receiver ofclaim 5, wherein the processor and the radio are further configured to:receive a second polar coded message in a wireless manner from thetransmitter; and subsequent to aborting the decoding procedure on thefirst polar coded message, implement the decoding procedure on thesecond polar coded message.
 10. The receiver of claim 5, wherein theprocessor comprises a plurality of parallelized processing elements;wherein the radio and the processor are further configured to: receiveone or more additional polar coded messages in a wireless manner fromthe transmitter; and implement, by separate ones of the parallelizedprocessing elements; the decoding procedure on each of the received oneor more additional polar coded messages.
 11. The receiver of claim 5,wherein the processor comprises a plurality of parallelized processingelements; wherein said decoding procedure is a successive cancellationlist (SCL) decoding procedure; and wherein separate ones of theplurality of parallelized processing elements are configured to performdecoding procedures on separate respective bit paths of the SCL decodingprocedure.
 12. The receiver of claim 5, wherein, in implementing thedecoding procedure on the first polar coded message, the receiver isfurther configured to: continue the decode of the first polar codedmessage to produce the plurality of information bits based on adetermination that the result of the cross-correlation calculation isabove the cross-correlation threshold.
 13. A method for decoding controlinformation, comprising: by a receiver: receiving a first polar codedmessage in a wireless manner from a transmitter, the first polar codedmessage comprising an encoding of a plurality of frozen bits and aplurality of information bits; implementing a decoding procedure on thefirst polar coded message by: beginning decoding the first polar codedmessage to produce a subset of the frozen bits; performing across-correlation calculation based on the subset of the frozen bits anda corresponding subset of reference bits, wherein the reference bits arebased on an identifier of the receiver; aborting the decoding procedurebased on a determination that the result of the cross-correlationcalculation is below a cross-correlation threshold.
 14. The method ofclaim 13, wherein the reference bits are a pseudorandom sequence of bitsgenerated from the identifier of the receiver, wherein the pseudorandomsequence of bits is the same length as the plurality of frozen bits. 15.The method of claim 13, wherein the first polar coded message isreceived and the decoding procedure is initiated as part of a downlinkblind detection procedure.
 16. The method of claim 13, the methodfurther comprising: receiving a second polar coded message in a wirelessmanner from the transmitter; and subsequent to aborting the decodingprocedure on the first polar coded message, implementing the decodingprocedure on the second polar coded message.
 17. The method of claim 13,wherein the receiver comprises a plurality of parallelized processingelements; wherein the method further comprises: receiving one or moreadditional polar coded messages in a wireless manner from thetransmitter; and implementing, by separate ones of the parallelizedprocessing elements; the decoding procedure on each of the received oneor more additional polar coded messages.
 18. The method of claim 13,wherein the receiver comprises a plurality of parallelized processingelements, wherein said decoding procedure is a successive cancellationlist (SCL) decoding procedure, and wherein said performing said decodingprocedure comprises implementing, by separate ones of the plurality ofparallelized processing elements, decoding procedures on separaterespective bit paths of the SCL decoding procedure.
 19. The method ofclaim 13, wherein the decoding procedure is a successive cancellationlist decoding procedure; and wherein said cross-correlation calculationcomprises calculating a divergence of path metrics associated with thesubset of decoded frozen bits and the corresponding subset of referencebits.
 20. The method of claim 13, wherein implementing the decodingprocedure further comprises: continuing decoding the first polar codedmessage to produce the plurality of information bits based on adetermination that the result of the cross-correlation calculation isabove the cross-correlation threshold.